This invention relates to the preparation of ceramic materials or articles by the pyrolysis of preceramic silazane polymers wherein the preceramic silazane polymers are rendered infusible prior to pyrolysis by treatment with steam or a steam and oxygen mixture. This method is especially suited for the preparation of ceramic fibers.
The prior art discloses that ceramic materials have been prepared by the pyrolysis of preceramic silazane polymers. Gaul in U.S. Pat. No. 4,312,970 (issued Jan. 26, 1982) obtained ceramic materials by the pyrolysis of preceramic silazane polymers, which polymers were prepared by reacting organochlorosilanes and disilazanes. The preceramic silazane polymers were pyrolyzed in an inert atmosphere without any separate treatment to render the silazane preceramic polymer infusible.
Gaul in U.S. Pat. No. 4,340,619 (issued July 20, 1982) obtained ceramic materials by the pyrolysis of preceramic silazane polymers, which polymers were prepared by reacting chlorine-containing disilanes and disilazanes. Fibers prepared from such preceramic silazane polymers were given a "mild heat treatment" in air before pyrolysis but there is no teaching that such a treatment rendered the fibers infusible.
Cannady in U.S. patent application Ser. No. 555,755, filed Nov. 28, 1983 obtained ceramic materials by the pyrolysis of preceramic silazane polymers, which polymers were prepared by reacting trichlorosilane and disilazane. The preceramic silazane polymers were not rendered infusible prior to pyrolysis, in order to form ceramic materials.
What has been discovered is a method of rendering preceramic silazane polymers infusible prior to pyrolysis. This method represents a significant advance in the art of preparing ceramic materials or articles, especially in the art of preparing ceramic fibers.